Master cylinder for hydraulic brakes



Aug. 20, 1940- o. RASMUSSEN MASTER CYLINDER FOR HYDRAULIC BRAKES Filed Sept. 28, 1938 k Qa Wg Jnventor 014/ Wqsmussen I attorney um'rlzo STA'TES PATENT OFFICE MASTER CYLINDER FOR HYDRAULIC BRAKES Olaf Rasmussen, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporatlon ogelaware Application Sc tember 28, 1938, Serial No. 232,071

2 Claims. (Cl. 6o54.6)

Such systems are in common use for applying The master cylinder is of that kind wherein brakes. These systems employ a master cylinder fluid is displaced by the movement of a plunger 5 within which the movement of the fluid column is 3| reciprocable therein. I The plunger carries no initiated, and, associated with the master cylsealing cup sliding along the cylinder wall but inder, is a rese oir adapted to communicate with is sealed by a reinforced rubber cup as at 33 at the master cylinder under certain conditions of the end gg/thecylindrical portion H1. The plunguse. The present invention is more especially er proje s through that part of casting H whi h 10 concerned with the control of the passage beextends through the floor 7 and is sealed as at tween the master cylinderand the reservoir in 35 and is provided with a dust guard 31.

such systems. It has been designed particularly end of the plunger carries a foot pad 39. Jointed nd 4 is sho or an installation in connection with hydraulic linkage 4| a h age func rakes but it may be used in installations where oils to prevent rotation of the plunger under he movable column used to release clutches, t e 00 the operator At the joint 45 1s a shift gears or do other useful work. spring 41 which surrounds the joint and has its the master cylinder. A secondary object is the into the master cylinder and it serves as a re- 2 Other objects and advantages will be understood b y m n a up 4 his up s p s d f r-- from the following description. ward by a spring 5t seated against the seal 33 25 Figure 1 is a longitudinal sectional view ages the extreme end of the extension 2|. The showing a master cylinder and reservoir with the cup 49 has, therefore, a limited sliding movement invention embodied therein. engaging, as stated, the end of the extension 2! 3 e 2 is a similar section of a portion f at one end of its movement and a shoulder 53 Figure 1 but on an enlarged scale and with cerat the other end of its movement. tain of the parts displaced from the position h W f casting ll etween the'reservoir shown in Figure 1. Y and the master cylinder is formed with a passage Figures 3 and 4 are longitudinal sections of a 55 in o w i h is thr aded a plug 51. The plug 3 modified form, the two figures showing their movis apertured to provide clearance between the wall as able parts in changed positions. of its aperture and the stem of a valve 6|. The

Referring to Figures 1 and 2, the numeral 1 is valve carries a sealing ring 63 adapted to seat applied to the floor of the operators compartag in t he ott m of plug 51 around its aperture ment of a motor vehicle. Secured to the floor under the influence of a spring 65 seated upon by fastening means 9 is a casting H which prothe plug and engaging an abutment 61 secured to 40 ,iects through a floor board opening [3. This the valve stem. The valve has a head 69 formed casting H is formed with a chamber or reservoir W! h a tapering surface 1|. This head is located 15 closed by a removable cover H. The casting wi hin an opening 13 in the wall of cup 49. The

5 into portion I9 is a closed tubular eiztension 2i. with a tapered wall 15 which taper is intended 0 inders. To that end the outlet opening 23 has the valve communication is established between used to maintain a limited degree of pressure in ing such movement of the plunger an abutment the conduit and wheel cylinders when the plunger 11 carried thereby picks up the bottom wall of the cup 49 and moves it against the resistance oi spring 5 Figure 1 shows the positions assum d by the parts when the brake is released. To apply the brakes the plunger is pressed downwardly into the master cylinder. Fluid is iorced therefrom through the conduit 21 to the wheel cylinders. when the pressure on the pad is relieved .the plunger is returned under the influence of spring M. It may be that the plunger returns too rapidly to permit the fluidirom the wheel cylinders to overcome the tendency to vacuum in the massand fluid from the reservoir to the master cylinder. when the plunger approaches its outward limit it picks up and moves the cup 49 as stated above, moving position shown in Figure 2 to the position shown in Figure 1. In the process or so moving the c p its beveled edge I5 engages the angular face of the valve I8 and opens the valve in a way which will be obvious upon inspection oi the drawing.

Figures 3 and 4 show a modified form. In

these forms the casting li' corresponds to cast- The extension 1| corresponds 2|. The opening for dischargeto the conduit is shown at 23'. Instead of the valved communication between the reservoir and the master cylinder there is a communicating passage 8|. A spring 83 is seated against the washer 33' as in Figure 1 and forces a metal cup 85 against the end of the extension 2|. In the cup 85 are openings permitting free passage of f1 The metal cup carries a flanged sealing member, the like, 01. The wall of the metal cup may have recessed portions 89 to permit the rubber to be deflected inwardly oi the cup. when advanced into the cylinder the ll and the displaces fluid from the master cylinder through the conduit. When the plunger is in retracted position as shown by Figure 4 iree communication between the reservoir and the master cylinder may occur. when the plunger is being advanced the spring 83 causes the passage 8! to be closed. As the plunger advances pressure in the master cylinder tends to increase and no fluid may pass to the reservoir. when the plunger withdraws any tendency to vacuum is overcome by the passage through communibeing deflected when the pressure is fully withdrawn tree communication between the reservoir and master cylinder is reestablished.

I claim:

1. A master cylinder, a plunger therein, a reservoir, there being a passage between said reservoir and cylinder, a valve to control said passage, and means engag by and movable said valve in the retracted position of the plunger, said means including aperture in its wail, yielding means to move said cup to a position wherein it is inoperative upon said valve, the wall of said operture being adapted to engage the head oi said valve to open the same when the cup is moved by the plunger to its retracted position.

2. A master cylinder, a plunger reciprocable a reservoir, there being a passage bereservoir and cylinder, a valve to control said passage, and means engaged by and open said valve in the retracted position of the plunger, said means reciprocable yielding wherein said valve having cooperating angular faces.

OLAF RA MUSSEN. 

